An Ocean Trap for Carbon Dioxide

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Schrag argues that drilling an escape route for water that has remained trapped in the porous rock for millions of years will help ease the pressure on the rock. "This ancient seawater is very similar to modern seawater, so there should be no ecological impact from letting it out," he says.

The release of seawater from the rock will raise sea levels over time, but not by much, says Schrag. The four million tons of CO2 produced by the plant each year will only cause about a micrometer rise in seawater over 100 years. Even if 1,000 coal plants began sequestering carbon offshore, sea levels should only rise by a millimeter during this time frame, Schrag says.

Dave Goldberg, a research scientist at Columbia University's Lamont-Doherty Earth Observatory, agrees that the idea is sound but says that any pilot project should be carefully shepherded to make sure that there is no harm to the ecosystem. The ocean is so vast that injecting CO2 shouldn't raise water levels much, either by lifting the floor or displacing trapped water, he says, but the bacterial ecology might potentially be changed. "Water slowly percolates through the rock at the bottom of the ocean in many places," Goldberg says. "The impact of speeding this up and introducing new opportunities for water movement is an open research question."

Carbon sequestration remains a controversial issue, however, and many environmental groups worry that it could allow coal plants to earn approval ahead of cleaner energy technologies. Another concern is how sequestration will impact ocean wildlife.

Whether carbon sequestration will become a reality will also be an issue of politics. Schrag was recently appointed to President Obama's Council of Advisors on Science and Technology. Schrag says that carbon sequestration should be one of several ways to combat climate change. "We need it all," he says. "We need renewables, we need better energy efficiency, we need energy conservation, and we need carbon sequestration."